The semiconductor integrated circuit (IC) industry has experienced rapid growth. Technological advances in IC materials and design have produced generations of ICs, where each generation has smaller and more complex circuits than the previous generation. In the course of integrated circuit evolution, functional density (i.e., the number of interconnected devices per chip area) has generally increased while geometry size (i.e., the smallest component or line that can be created using a fabrication process) has decreased. When the width of a conductive line becomes smaller, the unit-length resistance of the conductive line becomes greater, and vice versa. In some applications, a digital signal transmitted on a conductive line has a longer rising or falling time when the unit-length resistance thereof becomes greater. In other words, the unit-length resistance of a conductive line limits an operating frequency of a digital signal transmitted thereon.